Shot cartridge with tracer means



y 8, 1964 E. GRINZENBERGER Q 3,142,254

HOT CARTRIDGE WITH TRACER MEANS Filed May 29, 1961 2 Sheets-Sheet 1 y 28, 1964 I E. GRINZENBERGER 3,142,254

SHOT CARTRIDGE WITH TRACER MEANS Filed May 29, 1961 2 Sheets-Sheet 2 FIGS J J Q Q Q J M// INVENIOR:

ERm-r G'R/NZENBEEGER,

WIS ATTORNEY 3,142,254 SHQT CARTREBGE WITH TRACER MEANS Ernst Grinzenherger, Vienna, Austria, assignor to Alois Charwat, Vienna, Austria Filed May 29, 1961, Ser. No. 113,454 Claims priority, application Austria May 30, 1960 4 Ciairns. (Cl. 102-42) This invention relates to a shot cartridge which comprises a smoke capsule containing a substance which produces a smoke trace. Shot cartridges comprising smoke capsules which produce a smoke trace are known but in these cartridges the smoke capsule is arranged so that its charge is ignited by the charge of the shot cartridge when fired. This requires a special design of the shot cartridge because the wad must have an igniting duct and the smoke capsule must be held in position in the shot cartridge at the opening of this igniting duct. Besides, the smoke capsule must be open to enable its ignition and the opening of this smoke cap must obviously face the igniting duct. Such designs are complicated and require a special construction of the shot cartridge.

It is an object of the invention to provide a shot cartridge which comprises a smoke capsule and which is free of these disadvantages. The invention resides essentially in that the smoke capsule is formed by a closed hollow body, which is suitably ball-shaped and is loosely inserted in the shot charge. When designed according to the invention, the smoke capsule may be introduced into any desired shot cartridge without alteration of the design thereof and the construction in the form of a closed hollow body enables the arrangement of the smoke capsule at any desired point of the shot charge so that the trajectory of this smoke capsule will roughly mark the axis of the sheaf of small shot. The position required to accomplish this object may be empirically determined. It is desirable to arrange this body at the center or the center of gravity of the shot charge. The ball shape of this smoke capsule affords the advantage that its flight conditions can easily be adapted to those of the shot.

In a preferred embodiment of the invention the hollow body forming the smoke capsule contains a substance which will produce smoke when contacted by air and this hollow body is airtightly sealed and has portions which tend to form a leak under the firing pressure.

It is thus ensured that the development of smoke will automatically begin at the time of firing whereas measures for ignition are not required. The hollow body consists suitably of sheet metal, such as copper or brass.

To fulfil the requirement that the initially airtight hollow body becomes untight under the discharge pressure, this hollow body according to the invention may be formed with slots which are closed by a substance which will not withstand the firing pressure, such as shellac. According to the invention, this hollow body having the shape of a ball may have crossing slots extending from the two points of intersection of a ball axis, the crossing slots extending from the two points of intersection of the ball axis being relatively staggered. This hollow body is slightly deformed when the cartridge is fired. This is sufficient, however, to break the seal of these crossing slots, e.g., the shellac coating applied to this hollow body, and the admission of air will cause the evolution of smoke to mark the trajectory.

The smoke capsule should mark the trajectory of the sheaf of shot and for this reason flight qualities should be equal or similar to those of the granlues of shot themselves. On the other hand, the specific gravity of the smoke capsule is smaller than that of lead and it has been found that the requirement that the trajectory should be equal or similar can be more easily fulfilled if the diam- 3,142,254 Patented July 28, 1964 eter of this smoke capsule is about twice the diameter of the shot.

An illustrative embodiment of the invention is diagrammatically shown on the accompanying drawing.

FIG. 1 is an elevation showing a hollow body which contains the substance that produces the smoke trace. FIG. 2 is a top plan view thereof and FIG. 3 is an elevational view partly in cross-section of a shot cartridge according to the present invention.

Referring to FIG. 3 of the drawing, the shot cartridge C according to the present invention comprises a cardboard shell 7 which contains a powder charge 9 and a shot charge 6 the two charges being separated by a wad 8 of felt or the like material. Embedded in the shot charge 6, preferably at the center of gravity thereof, there is a smoke capsule 1. The shot charge 6 is held in position within the cardboard shell 7 by means of a cover 10 in a manner known per se.

The smoke capsule 1 consists of thin sheet brass or copper and is ball-shaped. Crossing slots 4 and 5 extend from the two points of intersection 2 and 3 of a ball axis. The crossing slots 5 are staggered by 45 from the crossing slots 4. These crossing slots extend somewhat beyond the center of the ball. Such a hollow body may be made by drawing from sections of a small tube, which have been provided with appropriate cuts.

When this ball-shaped hollow body has been filled with the substance which produces the smoke trace, e.g., white phosphorus, it is coated with shellac 1a, which tightly seals slots 4 and 5 and will become untight only under the firing pressure.

This smoke capsule 1 has a lower specific gravity than the granules of shot made from hard lead. The ratio between the diameters of the smoke capsule and the shot granule is so chosen that the retardation of both bodies in flight due to the air resistance is equal so that both bodies have the same trajectory. According to Prandtl, (Ballistik by Richard Emil Kutterer, 3rd edition, 1959 Friedr. Vieweg u. Sohn, Braunschweig, page 26, and Oerlikon- Taschenbuch 1956, copyright by Werkzeugmaschinenfabrik Oerlikon Buhrle u. Co., Zurich-Oerlikon, page 163) the air resistance equals where W is the air resistance, c the resistance coefiicient which depends on the shape of the missile, the velocity, and the viscosity of the air, Q is the air density, V the velocity of the missile, G the weight of the missile, F the largest cross-section of the missile, w the retardation of the missile, in the mass of the missile. Hence, the retardation w of the missile equals to =g=cw X g V Xg (meters seconds where G/F is the weight per unit of cross-section.

Thus, the retardation is inversely proportional to the weight per unit of cross-section.

Since the smoke capsule and the shot granules are shot in the same air atmosphere and have the same spherical shape and are shot at the same velocity, they have also the same resistance coefficient c The same retardation of the missile and the same trajectory of both bodies will be obtained, therefore, when both have the same weight per unit of cross-section. The diametral ratio must be determinad so that the latter requirement is fulfilled and for a shot diameter of 2.5 mm. equals 2.04 so that the hollow body 1 has a diameter of 5.1 mm. A hollow body 1 of this size having an envelope of brass sheet 0.8 mm. thick has a somewhat larger load per unit of cross-section if the slight increase in air resistance due to the crossing slots is considered and will, therefore, de-

scribe the same trajectory. The charge consists of 0.041 gram phosphorus in the form of a ball 3.5 mm. in diameter.

In the embodiment described by way of example, the weight of 'the smoke capsule (includingthe phosphorus charge) is 0.40 gram, that of the shot granule is 0.0915 gram so that the smoke capsule having approximately the same load per unit of cross-section and 2.04 times the diameter of the shot ball has 4.4 times the weight of the latter.

What I claim is:

1. A shot cartridge for a firearm,'comprising a shot charge, a closed, ball-shaped, hollow body having apertures and being embedded in the center of gravity of said shot charge, and a substance capable of producing smoke when contacted by air, contained within said hollow body, and means airtightly sealing said apertures and leaking under the firing pressure.

2. A shot cartridge for a firearm, comprising a shot charge, a closed, ball-shaped hollow body embedded in said shot charge, and a substance capable of producing smoke when contacted by air, contained within said hollow body, said hollow body consisting of sheet metal and being provided with slots, and a substance which will not withstand the firing pressure sealing said slots.

3. A shot cartridge for a firearm, comprising a shot charge, a closed ball-shaped hollow body embedded in said shot charge, and a substance capable of producing smoke when contacted by air, contained within said hollow body consisting of sheet metal and having crossing slots extending from the two points of penetration of a ball axis through the ball surface, said crossing slots being relatively staggered, a substance which will not withstand the firing pressure covering said slots.

4. A shot cartridge for a firearm, comprising a shot charge, a closed, ball-shaped, hollow body having apertures and being embedded in said shot charge, and a substance capable of producing smoke when contacted by air, contained within said hollow body, and means airtightly sealing said apertures and leaking under the firing pressure.

References Cited in the file of this patent UNITED STATES PATENTS 1,144,379 Pritham June 29, 1915 1,191,178 Harrison et al July 18, 1916 1,305,113 Jewett May 27, 1919 1,305,115 Jewett May 27, 1919 1,363,043 Jewett Dec. 21, 1920 2,368,029 Knight Jan. 23, 1945 2,381,474 Turnbull Aug. 7, 1945 

1. A SHOT CARTRIDGE FOR A FIREARM, COMPRISING A SHOT CHARGE, A CLOSED, BALL-SHAPED, HOLLOW BODY HAVING APERTURES AND BEING EMBEDDED IN THE CENTER OF GRAVITY OF SAID SHOT CHARGE, AND A SUBSTANCE CAPABLE OF PRODUCING SMOKE WHEN CONTACTED BY AIR, CONTAINED WITHIN SAID HOLLOW BODY, 